Each year, about 40,000 children are adopted across national lines, primarily by families from North America and Western Europe. These joyful occasions mark the growth of new families and also provide the framework for a natural experiment in language development. Although most are infants and toddlers, thousands of older children are also adopted. Typically, these older children lose their birth language rapidly and become fluent speakers of their new language.
Jesse Snedeker of Harvard University believes that these older children can help us understand how infants learn their native language. Early language development follows a predictable series of milestones. Babies initially say one word at a time, and mostly use nouns ("ball") or social words ("hi"). As they grow older their sentences become longer and more complex, as verbs ("take") and grammatical words ("about") begin to appear.
These changes in the infant speech could be due to the child's increased cognitive abilities or, as Snedeker asserts, they might also simply be side effects of the learning process itself and independent of the child's age or cognitive abilities. For example, it might be easier for children to learn the meanings of nouns because they often refer to things that we can point to or look at.
To explore the role of cognitive maturation in language development, Snedeker and her colleagues tracked the acquisition of English in children who were adopted from China between 2 ½ and 6 years of age. The researchers followed the children's progress during their first year in the U.S. and compared them with infants who were learning English as a first language.
Studying internationally-adopted children was vital to this research because their language development is often out of sync with their cognitive development and maturation. Internationally adopted preschoolers begin learning one language and then move to a home in which a different language is spoken. Unlike most second language learners, they have no phrase book to consult or bilingual informants to translate what they hear. In many ways their situation is like that of infants learning their first language: they must discover the meanings of words by listening and watching what happens around them. But they differ from infants in one critical respect--they are older and thus more cognitively mature.
Snedeker found that the preschoolers went through the same stages as the infants. Early on they learned many nouns but few verbs or grammatical words. Like the infants, the preschoolers initially produced one word utterances, followed by short telegraphic sentences ("Mommy eat"). Snedeker and colleagues also found that the adopted children progressed through the stages more rapidly than the infants, which is good news because it suggests that many of these children will eventually catch up with their peers.
These findings, which appear in the January 2007 issue of Psychological Science, indicate that the stages used to characterize infant language development are not solely attributable to cognitive development and maturation. Children who are much older and more mature go through these same stages when they learn a new language via immersion in speech. Snedeker concludes that these stages are side effects of the processes children use to learn words and grammar.